Manufacturing process of cold rolled steel pipe

Cold rolling, done often at room temperature, has the added effect of work hardening and strengthening the material thus further improving the material’s mechanical properties. It also improves the surface finish and holds tighter tolerances. However, room temperature steel is less malleable than hot steel, so cold rolling cannot reduce the thickness of a work piece as much as hot rolling in a single pass. Commonly cold-rolled products often include similar hot rolled products like sheets and bars, but are usually smaller.

What are commonly used heat treatments, purposes and scope of application of steel pipes in cold drawn and cold rolled production?

Heat treatment is an important part in cold drawing and cold rolling of steel pipes. During the production process, heat treatment of steel pipes can be classified into tube billets heat treatment, intermediate tube heat treatment and finished tube heat treatment according to the process. Methods, purposes and scope of application of heat treatment for steel pipes are as the following table.

Normalizing and high temperature tempering and annealing and tempering

Eliminating internal stress, improving toughness of the material and obtaining high strength and hardness

Low alloy structural steel

Finished pipe heat treatment

What are the purpose and methods of pickling in the processing of cold-rolled steel pipes?

The oxide scale on the inner and outer surfaces of pipe billets should be removed before the cold drawn and cold roll processes. Methods of removing the oxide scale include mechanical methods such as shot blasting and polishing, chemical methods and electrochemical methods. The pickling method is used for removing the oxide scale on the surface of cold drawn and cold roll steel pipes. Pickling methods include sulfuric acid pickling, hydrochloric acid pickling, mixed acid pickling, hydrofluoric acid pickling and alkali-acid pickling. Sulfuric acid pickling is one of the most widely used methods. Sulfuric acid pickling is usually adopted for carbon steel and low alloy structural steel which don’t have special requirements.